sending e mail

I am developing a shopping cart, i want to inform buyer of the tracking number by sending an email as soon as they check out the material.
If somebody could suggest me a way....
I know i will have to use smtp...but i dont know if there is a way of doing this without using smtp. I looked into JavaMail but it also requires smtp server. correct me if i am wrong.
I have tomcat as my webserver, has cloudscape as an embedded database in tomcat on W2K.
I tried to use PostCast smtp server, freeware but couldn't make it work. Please suggest me a way.
thanks for the help